Examples

How It Works

Carbidopa is a medicine (called a decarboxylase inhibitor) that, when taken with levodopa, helps prevent the levodopa from converting to dopamine outside the brain. The combination of carbidopa and levodopa has several benefits:

It allows more levodopa to get to the brain and thus increases the supply of dopamine in the brain.

It decreases side effects caused by increased dopamine levels outside the brain by reducing the supply of "free" dopamine outside the brain. (Increased dopamine levels outside the brain can result in side effects such as nausea, vomiting, and low blood pressure.)

It enhances the effect of levodopa, so that less levodopa is needed to control symptoms.

Why It Is Used

Levodopa is a medicine used to control symptoms of Parkinson's disease and may be used at all stages of the disease.

How Well It Works

Levodopa is the most effective medicine for relieving symptoms of Parkinson's disease. It helps reduce tremor, stiffness, and slowness and helps improve muscle control, balance, and walking. It does not affect freezing, dementia, or problems with involuntary (autonomic) functions, such as constipation, urinary problems, impotence, or pain.1

Levodopa does not slow the disease process, but it improves muscle movement and delays severe disability. The use of levodopa allows people with Parkinson's disease to stay independent and able to function for longer periods of time. But the majority of people taking levodopa develop complications caused by long-term levodopa therapy within 5 to 10 years. Movement problems (motor fluctuations) are the most common and troublesome complication.

Side Effects

All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.

Here are some important things to think about:

Usually the benefits of the medicine are more important than any minor side effects.

Side effects may go away after you take the medicine for a while.

If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

The decision about whether it is better to use levodopa or a dopamine agonist as the first treatment in Parkinson's disease is different for each person. Levodopa controls symptoms better than dopamine agonists in most people. And levodopa has fewer side effects than dopamine agonists. But concern about levodopa-related motor fluctuations is leading some doctors to use dopamine agonists as initial therapy in people with newly diagnosed Parkinson's disease in order to delay treatment with levodopa. The American Academy of Neurology now recommends this approach for most people who have the disease.

In theory, the purpose behind delaying treatment with levodopa, especially in younger people with Parkinson's, is to delay the motor fluctuations that eventually occur with levodopa therapy. But in the long term, the same amount of people have motor fluctuations no matter what medicine is used first.2 If a dopamine agonist is used as initial therapy, levodopa may be added when the dopamine agonist is no longer able to control symptoms adequately on its own.

Levodopa may cause impulse-control disorders in some people. Impulse-control disorders include uncontrollable or problem gambling, sexual behavior, and shopping. Binge eating is another example.

Levodopa is less likely than dopamine agonists to cause impulse-control disorders. But your risk is even higher if you take both a dopamine agonist and levodopa. If you are concerned about taking these medicines because of this risk, talk with your doctor.

Taking medicine

Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.

There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.

Checkups

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

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